Air pollution causes about 200,000 early deaths each year in the United States, according to a new study from the Massachusetts Institute of Technology (MIT).

Researchers at MIT’s Laboratory for Aviation and the Environment, say emissions from road transportation are the leading single cause of pollution, contributing 53,000 premature deaths, and that electrical power generation causes another 52,000.

“In the past five to 10 years, the evidence linking air-pollution exposure to risk of early death has really solidified and gained scientific and political traction,” says Steven Barrett, an assistant professor of aeronautics and astronautics at MIT. “There’s a realization that air pollution is a major problem in any city, and there’s a desire to do something about it.”

Baltimore, Maryland, was the city with the highest emissions-related death rate in the United States, with 130 out of every 100,000 deaths likely caused by exposure to air pollution.

According to Barrett, a person who dies from air-pollution causes typically dies about a decade earlier than he or she might have otherwise.

The study was done using data from the Environmental Protection Agency’s National Emissions Inventory, a catalog of emissions sources nationwide. The data was from 2005, the most recent available.

That data was divided into sources of pollution: electric power generation; industry; commercial and residential sources; road transportation; marine transportation; and rail transportation. Then, using an air-quality simulation, they were able to determine which source had the greatest impact and in what parts of the country.

Most premature deaths -- due to commercial and residential pollution sources, such as heating and cooking emissions -- occurred in densely populated regions along the East and West coasts. Pollution from industrial activities was highest in the Midwest, roughly between Chicago and Detroit, as well as around Philadelphia, Atlanta and Los Angeles. Industrial emissions also peaked along the Gulf Coast region, possibly due to the proximity of the largest oil refineries in the United States.

Pollution from electricity generation still accounted for 52,000 premature deaths annually. The largest impact was seen in the east-central United States and in the Midwest: Eastern power plants tend to use coal with higher sulfur content than Western plants.

Southern California had the largest health impact from marine-derived pollution, such as from shipping and port activities, with 3,500 related early deaths. Emissions-related deaths from rail activities were comparatively slight, and spread uniformly across the east-central part of the country and the Midwest.

“It was surprising to me just how significant road transportation was,” Barrett said, “especially when you imagine [that] coal-fired power stations are burning relatively dirty fuel.”

One explanation may be that vehicles tend to travel in populated areas, increasing the pollution exposure of large populations, whereas power plants are generally located far from most populations and their emissions are deposited at a higher altitude.

While the study is based on data from 2005, Barrett says the results are likely representative of today’s pollution-related health risks.

“A public-health burden of this magnitude clearly requires significant policy attention, especially since technologies are readily available to address a significant fraction of these emissions,” said Jonathan Levy, a professor of environmental health at Boston University, who was not involved in the research. “We have certainly invested significant societal resources to address far smaller impacts on public health.”

Barrett and his colleagues published their results in the journal Atmospheric Environment.